The following relates generally to wireless communication, and more specifically to asymmetric downlink-uplink transmission time interval (TTI) configurations for low latency operation.
Wireless multiple-access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is designed to improve spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards. LTE may use orthogonal frequency division multiple access (OFDMA) on the downlink, single-carrier frequency division multiple access (SC-FDMA) on the uplink, and multiple-input multiple-output (MIMO) antenna technology.
In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In a LTE or LTE-Advanced (LTE-A) network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation new radio (NR) or 5th Generation (5G) network), a wireless multiple access communication system may include a number of smart radio heads (RHs) in communication with a number of access node controllers (ANCs), where a set of one or more RHs, in communication with an ANC, defines a base station (e.g., an eNB or giga-nodeB (gNB)). A base station may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
A base station in some LTE or NR deployments may transmit to one or more UEs using different length TTIs that may be reduced in length relative to legacy LTE TTIs. Such a reduced length TTI may be referred to as a shortened TTI (sTTI) and users communicating using sTTIs may be referred to as low latency users. An sTTI may be a subset of one or more subframes that correspond to legacy TTI subframes. A base station may allocate transmission resources for sTTIs to a UE that may include time resources, frequency resources, and one or more component carriers (CCs) to be used for sTTI transmissions. Efficient allocation of such resources for data, control information, and reference signal transmissions may help to increase the efficiency of a wireless communications system.